1. Field of the Invention
This invention is directed to the formation of novel polymeric fiber masses, the fibers therefrom and processes for producing the same. It also involves composites of said polymeric fiber masses in a solid polymeric matrix.
2. Description of Prior Art
In the past, polymeric fibers have frequently been made by drawing or extruding a viscous solution of the polymeric forming substance through a small orifice. The fibers are then stretched to orient them and increase their strength. Also, fibers are produced by extrusion of molten polymers. The resultant fibers are rarely less than 0.0001 inch (approx. 30,000 A) in diameter.
Fibers have also been formed by stirring a very dilute solution of the fiber-forming material. This procedure results in the formation of linear fibers attached to the stirrer (Pennings, A. J., et al., Polymere, 99 (1969). These fibers are non-uniformly distributed around the stirrer and are spirally arranged. The formation of similar fibers from stirred solutions has also been reported by A. Keller, (Physics Today, May 1970, page 42.) In addition, a crystalline material having a shish kebab structure has been formed by irradiating a dilute solution of polyethylene in p-xylene with ultrasonics at 0.1 to 0.4 mW/cm from 85 to 190 kilo Hz at a temperature between 82.degree. C. to 88.degree. C. The concentration of polyethylene in the solvent ranged from 0.05 to 0.5% by weight. (Blackadder and Schlenitz, Nature 200, 778 (1963)).
Recently, Gallacher in U.S. Pat. No. 3,796,778 has produced fibrous mats or web type structures which on superficial inspection seem similar to the fiber masses of this invention. Gallacher states that the structure of his fiber mat is a "web of oriented, interconnected, directional fiberlike strands, membranes, branched ribbons and fibrils".
The fibrous mats of Gallacher are produced from a heterogeneous, two phase mixture of two incompatible polymers. A mixture of two polymers is milled together while in a heated semi-liquid state. The fibrous mass and web-like interconnected structure is produced by mechanical drawing and shearing in the molten state of one of the polymers within the mass by the action of the two roll mill. The fibrous mat is then separated from the other matrix polymer by dissolving the matrix away with a selective solvent.
Also, in U.S. Pat. No. 3,778,294, Krauch and Sanner produced polymers having a fibrous polymeric structure for the reinforcement of non-woven fabrics. Their method is restricted to the formation of fibrous poromeric material from ethylenically unsaturated monomers with at least two polymerizable double bonds or mixtures containing at least 0.01% by weight of these monomers and ethylenically unsaturated monomers. Apparently, a quasi-fibrous structure is caused to occur by curing these monomers within the interstices among the crystals of a partially frozen or solidified solvent. Curing is caused to occur by irradiation with high energy light or ionizing radiation. The material is then thawed and the non-woven fabric reinforced polymeric material is separated from the solvent. Although Krauch and Sanner do not describe the morphology of their polymeric material precisely, they do indicate that their invention is limited to sheet-like or planar forms because of the necessity of efficient cooling and complete penetration of the irradiation. Also, they describe their material as a fibrous polymeric material from which it is deduced that porous or sponge-like characteristic exist in combination with some fibrous characteristics. The products are described as soft, leatherlike, and velvety.